How Long Does Polyresin Last?

When the resin and hardener are properly stored in airtight containers at room temperature to prevent contamination, the shelf life of epoxy resin can last for many years.

Anyone who has used polyester resin knows that it only has a shelf life of about six months before it turns into a useless jelly-like substance.  The initial cost savings from cheaper materials can easily be offset by large amounts of expired materials.  Fortunately, the epoxy resin we use has an excellent shelf life.  With proper storage and good housekeeping, you can always take your epoxy resin with you, no matter what the project brings.

Store epoxy resin and hardener at room temperature.  Keep container tightly closed to prevent contamination.  If stored properly, the resin and hardener should last for many years.  After long-term storage, verify the metering accuracy of the pump.  Mix a small test batch to ensure proper curing.

105 Resin will thicken slightly over time and requires extra care when mixing.  Repeated freezing/thawing during storage may cause 105 Resin to crystallize.  Heat the resin to 125°F (place the jar under a warm light or in a warm water bath) and stir to dissolve the crystals, just as you would with honey.

Curing agents, especially 205 Fast Curing Agent, may darken over time, but physical properties are not affected by color.  If it is a clear finish, be aware that color changes may occur if a very old and new hardener are used on the same project.

Overview of Epoxy Resin Shelf Life

Shelf life is the amount of time an epoxy resin can sit unused and still function as designed.  The shelf life of epoxy resin begins when the material is made.  We mixed our 15 year old WEST SYSTEM 105 epoxy with a new hardener and it cured well (see real life shelf life).  Although resins and hardeners that are several years old should cure as designed, you may want to reserve them for applications where strength or clarity are not particularly important.

The easiest and most accurate way to test problematic resins and hardeners is to conduct a simple pot life test.  Mix a total of 100 grams of resin and hardener (in appropriate proportions) in a 2-inch diameter container at 72°F.  Start timer and stir for 2 minutes, then set aside.  Don't leave it on as your body temperature will speed up healing and skew the results.  Be careful as large amounts of epoxy can generate high heat during the curing process.  When the epoxy gels, the pot life of the mixture is over.  If the resin and hardener are still good, they will cure within the "pot life" time indicated on the hardener container.

Epoxy resin and pot life as a function of temperature

 Epoxy resins and hardeners do not have a strict shelf life.  Some changes may make them less effective for certain jobs, but the resin and hardener are still reactive.  Since we are an ISO 9001 certified company, the containers are marked with a batch number and we retain each batch for up to 2 years from the date of production.  However, the actual shelf life is usually much longer.